Fischer-Tropsch (hereinafter F-T) synthesis was first developed by German chemists Hans Tropsch and Franz Fischer in 1925, and is a method for preparing a broad range of hydrocarbons using syngas (H2+CO) synthesized from major raw materials such as coal, natural gas, gas hydrate, or biomass by a reforming reaction. The process, a key component of the ‘gas to liquid (GTL)’ technology, usually accompanies side reactions such as the water-gas shift reaction, methanation reaction, Boudouard reaction, etc., but the main reaction is a polymerization reaction of carbon chains on the surface of a catalyst. There has always been a necessity for the technology of artificial oil production due to the threat of oil depletion, frequent changes in oil prices due to the political or economical situations of oil-producing countries, etc. Recently, the technology has drawn much attention as a technology to substitute oil as it considered to be a technology capable of producing a clean liquid fuel without a sulfur-containing component by utilizing the abundant feedstock such as the shale gas being newly discovered, and commercialization by major oil companies is underway.
Examples of the transition metals which are well known to show activities in the F-T synthesis reaction may include cobalt, iron, nickel, ruthenium, etc. However, Ru is too expensive to be used as a commercial catalyst (about 50,000 times more expensive than Fe) and Ni has a problem in that it has an extremely high selectivity for methanation, and thus only Fe and Co are used commercially.
In particular, a Co catalyst has a disadvantage in that it is about 200 times more expensive than a Fe catalyst. However, the Co catalyst is relatively cheap compared to noble metal catalysts and has higher catalytic activity in the F-T synthesis reaction than noble metal catalysts, and also has advantages in that it has a long life and high CO conversion, can inhibit the water-gas shift reaction, increase the selectivity of linear hydrocarbons, etc. Furthermore, the Co catalyst can show catalytic activities in the F-T synthesis at a temperature range lower than the Fe catalyst, and thus the Co catalyst has a large advantage as a catalyst for the F-T synthesis in terms of energy efficiency compared to the Fe catalyst.
However, since the activity of the Co catalyst is known to mainly depend on the number of active sites exposed to the surface, a process of uniformly dispersing Co, an active material, on top of a support having a very wide specific surface area is essentially required for obtaining a high catalytic activity, and thus a mesoporous material with a medium pore size is used as the most suitable material for the establishment of high dispersibility or a wide specific surface area of the catalyst.